The present invention is directed to fuel cells. More particularly, the present invention is directed to vehicles containing fuel cells, to methods for warming the fuel cells at low ambient temperatures, and to methods for reducing emissions of vehicles containing fuel cells.
A fuel cell is an electrochemical device that generates electricity from the electrochemical reaction between a fuel, such as hydrogen, and an oxidant, such as oxygen. Water is generally produced as a byproduct of this electrochemical reaction. Thus, it is important that water-producing fuel cells be maintained at temperatures above the freezing point of water in order to be operable and to prevent damage to the cells. Freezing can lead to mechanical strain on the cells and, thus, to reduced lifetimes.
To prevent freezing of a fuel cell when the ambient temperature approaches the freezing point of water, a strategy has been devised for applying a resistive load in parallel with the fuel cell (e.g., U.S. Pat. No. 5,789,092). However, such a method for warming the fuel cell entails considerable waste of power in the form of thermal energy, which is undesirable. An alternative strategy wherein the fuel cell is activated at low ambient temperature, and the electricity produced by the fuel cell stored in a battery is unsatisfactory because a limit in the storage capacity of the battery will eventually be reached. Thus, there remains the need to develop a method of warming a fuel cell in low ambient temperatures that avoids both the waste of power and the inadequacy of battery storage capacity.
It is appreciated in the art that a significant fraction (e.g., at least about 70%) of the unacceptable emissions produced by a vehicle equipped with a catalytic converter is generated in the period immediately following a cold start-up operation. Vehicles employing a fuel cell in the place of an alternator, as well as full-vehicle fuel cells incorporating a gasoline or methanol reformer, are both generally equipped with catalytic converters. Thus, both types of fuel cell-containing vehicles are subject to a period of high emissions following cold start-up. Once the catalyst attains its peak operating temperature, however, the corresponding vehicular emissions decrease significantly.
A strategy has been devised to reduce vehicular emissions by preheating the catalytic converter using electricity from the battery (e.g., U.S. Pat. No. 5,964,089). However, since the electrical load placed on the car battery during the pre-heating period may exceed the rated battery output and, at any rate, contributes to the shortened lifetime of the battery, a more practical solution is required. Similarly, pre-heating the catalytic converter using electricity from the alternator is an unsatisfactory solution because of the strain that is placed on the battery and because of the need for employing an oversized alternator (e.g., U.S. Pat. No. 5,964,089). Thus, there remains the need to develop a method for reducing vehicular emissions during the period following a cold start up which avoids the aforementioned problems.
In short, in vehicles containing a fuel cell, there are continued and pressing needs to develop methods for warming the fuel cell at low ambient temperatures, and for reducing vehicular emissions.
The scope of the present invention is defined solely by the appended claims, and is not affected to any degree by the statements within this summary. By way of introduction, the presently preferred embodiments described herein are directed towards remedying the aforementioned problems in warming fuel cells at low ambient temperatures, and in reducing vehicular emissions.
Briefly stated, a vehicle embodying features of the present invention includes a fuel cell that generates electricity, a pre-heater which provides an output and which is electrically coupled to the fuel cell, and a component configured to receive a portion of the output provided by the pre-heater, such that a temperature of the component is changed through receipt of the portion of the output.
A method for operating a fuel cell in a vehicle embodying features of the present invention includes generating electricity from the fuel cell, and providing a portion of the electricity to a pre-heater, which provides an output to a vehicular component, thereby pre-heating the component.
A second method for operating a fuel cell in a vehicle in accord with the present invention includes measuring a temperature, activating the fuel cell when the measured temperature is below a minimum set point, generating electricity from the fuel cells and providing a portion of the electricity to a pre-heater, which provides an output to a vehicular component to pre-heat the component.
A third method for operating a fuel cell in a vehicle in accord with the present invention includes measuring a temperature, generating electricity from the fuel cell, providing a portion of the electricity to a pre-heater, which provides an output to a vehicular component to pre-heat the component, decreasing the portion of electricity provided to the pre-heater when the measured temperature is below a minimum set point, and increasing the portion of electricity provided to the pre-heater when the measured temperature is above a maximum set point.